The snow-like hash on an analogue television is caused by background radiation from the Big Bang, the explosion 13.8 billion years ago which led to the formation of the Universe. But the Big Bang and the inflation of the universe which followed is presently just a theory. Darcy Barron's work has the potential to produce evidence which would turn theory into fact.

Transcript

Robyn Williams: Well, of course it did not sound like that, the Big Bang. No air to conduct, no ears to listen. But if you do want to observe it, just to turn on the telly, if you still have an old one, not digital. Our PhD this week is actually a graduate student, and she observes the microwave echo of the Big Bang 5,000 metres up a mountain in Chile. Darcy Barron is at the University of California, San Diego.

Remind me about the background radiation and the fact that in the old days when you turned on your television and got hash that was a signal saying, 'by the way, this is a reminder of the Big Bang'. Is that right?

Darcy Barron: Right, that's true. So the Big Bang happened, this big fireball, and the radiation from that is still getting to us now, you can still see that, there is about 400 photons per cubic feet around you right now. So it's this constant thing, if you look back to the right frequency, red-shifted all the way down into the microwave now, just completely uniform background, and yes, it's part of the hash on your TV if you have an analogue TV.

Robyn Williams: You'd imagine that after 13.8 billion years it would have faded away and we wouldn't have much of an afterglow.

Darcy Barron: Right, it has faded very far, and it's a much longer wavelength, red-shifted down to about a millimetre, but it is still pretty strong, it's still cooling but you can still see it. It is the coldest thing in the universe, you know, this is now this background temperature, it's not absolute zero, there is still this remaining 2.7 Kelvin.

Robyn Williams: That's cold, isn't it! And of course the discovery was made something like 50 years ago almost by accident, and two guys got a Nobel Prize for it. Why are you still looking for it now?

Darcy Barron: So they discovered it in the '60s, they thought it was just this weird noise they couldn't get rid of, but they talked to some scientists who said this is something we've been looking for, think of all these things that maybe you'll be able to find, and then we built instruments to try to go after that and find these details in it. The latest thing is the polarisation of this background and getting into details with that with these special detectors, detecting the polarisation of the radiation and looking for patterns in it and looking for these details that haven't been found yet.

So this past year the South Pole telescope is the first one to detect this pattern of the B mode polarisation, this specific pattern that traces back to the effects of gravity on the CMB basically, seeing the photons that have travelled for 13.8 billion years all the way here have been subtly deflected by all the matter in the universe, and so you can see that signal for the first time. So that's the next step right now, finding out different properties of the universe, things like the mass of the neutrino. A map of all the matter in the universe, these are things that we know now. With time, with the instruments we have, we will be able to do this.

Robyn Williams: You mean a map of all the matter in the universe? That's boggling.

Darcy Barron: Right. So the CMB is unique because it is back-light that was formed at exactly the time…it was before anything formed in the universe. So it's this back-light tracing past all the galaxies, all the dark matter that exists. So you can map all the matter in-between us and the beginning of the universe.

Robyn Williams: When will we know that you've got it?

Darcy Barron: So what we do, it's very difficult. We're very limited by the photons coming to us. We've got these great detectors, you just need to keep them on the sky for years at a time to map out the whole sky. So a survey would take a very long time. There are satellites, WMAP and Planck, who have started this, it's sort of like a five-year campaign.

Robyn Williams: Darcy, what is your particular role in this quest?

Darcy Barron: I'm a graduate student, and we have this new telescope in the Atacama Desert in Chile, so it's a small collaboration, we keep it running ourselves, so we send grad students about a month or two out of the year. You head up to 17,000 feet, drive up there in the truck and try to keep the telescope running basically. So again, we are trying to get as much data as possible, so we just need to keep our telescope on the sky for two or three years to get all the data we need.

Robyn Williams: What's it like there, because it's supposed to be the driest part of the Earth, is it not? It hardly rains there for decades on end.

Darcy Barron: Right, it's supposed to be very dry, although we've had a lot of problems with big snowstorms lately. So it's a lot like Mars, it's this very weird desert landscape. It's actually very flat on this plateau, it's the ALMA site, there are a lot of telescopes there. But it is, it's 17,000 feet, so it's very harsh. You have to wear sunglasses. The sun is just so bright. It's sort of crazy, we've got this self-contained site, you drive up this very long rocky road to your site, you've got a couple of shipping containers and the telescope, and that's it.

Robyn Williams: What do you do for fun up there?

Darcy Barron: You're in the mountains, so there's a lot of hiking and stuff to do, climbing, but yes, driving around in the truck.

Robyn Williams: Climbing in that sort of altitude…are you affected badly at all by the altitude sickness?

Darcy Barron: At that altitude everyone is affected. So if you are actually working you need to wear oxygen, you can't think straight without oxygen. It's down to about a third of the oxygen at sea level, so we have these little backpacks with a little hose going to your nose. But even at where we sleep it's 10,000 feet, 9,000 feet, so even if you are running around there, things are difficult.

Robyn Williams: Well, you obviously enjoy it…do you?

Darcy Barron: Yes, definitely. I think there is sort of a split between our group; there's the ones who really like it, the outdoors people who like to be in the mountains and running around, and the people who are, 'I'm just a scientist, I don't want to be here, what am I doing here?'

Robyn Williams: And the results of course will be terribly exciting. Do you think when you've got a lot of this work wrapped and you've understood the background radiation it will be a turning point, one of the turning points in astronomy?

Darcy Barron: I think so. I think there's a lot more to find out about the early universe, so this idea of inflation, the Big Bang happened and then the universe suddenly rapidly expanded, it's been a theory for 30 years now but we have no direct evidence for it. So this would finally be…here is evidence, this really happened, this isn't just some theory that seems to explain things, here's proof. So I think that would be big.

Robyn Williams: Darcy Barron in physics at the University of California, San Diego. And just imagine being there on your own with maybe an engineer, 5,000 metres up a mountain in Chile with only the student from the next telescope for company for a month.

Graham Wilson :

03 Mar 2014 1:50:04am

It really is a big stretch to say that the snow (noise) on the average domestic old-fashioned analogue TV comes from the Cosmic Microwave Background (CMB) radiation. Sure, there is some but it is minuscule. (If it were actually significant then the CMB would have been discovered long before Penzias and Wilson discovered it in 1964 with their large exotic horn antenna operating at microwave frequencies.)

Most of the noise in an analogue TV is produced from within the TV itself, especially on the higher channels. You can test this for yourself by disconnecting the antenna from the TV and you'll notice that the screen is still 'snowy' and the audio produces a rushing sound. In fact, if you reconnect the antenna on a blank channel you'll see very little increase in noise, and most of that increase is interference from the local electrical environment.

The noise produced in a TV set comes from the set's RF (radio frequency) amplifiers not being perfect—and even if the amplifiers were perfect then there'd still be noise but not just as much. Unfortunately, the laws of thermodynamics insist in stepping in and causing problems. At room temperature, ≈300 Kelvin, electrons are so hot they rattle around in the TV's electronics making so much noise you'd think they were ball bearings rotating in a kerosene drum.

Here, temperature is the big one! The CMB's temperature is only ≈2.7K and room temp is ≈300K. Shove these values into the Johnson/Nyquist thermal noise equation and simple multiplying will show the difference:

The essence of all this is that the electronic noise produced in a room temperature TV almost completely swamps the CMB noise which has a tiny equivalent noise temperature of only a few degrees above absolute zero (physicists don't split hairs, I know I've simplified this a bit for discussion).

Moreover, if you look at NASA's power distribution versus frequency graph for the CMB you'll notice that at TV channel frequencies (≈0.1-1GHz) the CMB's amplitude is orders of magnitude down from its peak (thus the energy distribution is very weak at these frequencies):

http://asd.gsfc.nasa.gov/archive/arcade/cmb_spectrum.html

TV channels (≈0.1-1GHz) are on the far LHS side, in fact the old ABC-TV CH2 is so far down (low in frequency) it's actually off the graph at ≈0.05GHz.